Re: [net-next PATCH v11 1/6] net: phy: pass PHY driver to .match_phy_device OP

[Christian Marangi <ansuelsmth@gmail.com>]

On Sat, May 17, 2025 at 10:28:04PM +0900, FUJITA Tomonori wrote:
> On Sat, 17 May 2025 10:09:53 +0200
> "Benno Lossin" <lossin@kernel.org> wrote:
> 
> > On Fri May 16, 2025 at 11:23 PM CEST, Christian Marangi wrote:
> >> diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
> >> index a59469c785e3..079a0f884887 100644
> >> --- a/rust/kernel/net/phy.rs
> >> +++ b/rust/kernel/net/phy.rs
> >> @@ -418,15 +418,18 @@ impl<T: Driver> Adapter<T> {
> >>  
> >>      /// # Safety
> >>      ///
> >> -    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
> >> +    /// `phydev` and `phydrv` must be passed by the corresponding callback in
> >> +    //  `phy_driver`.
> >>      unsafe extern "C" fn match_phy_device_callback(
> >>          phydev: *mut bindings::phy_device,
> >> +        phydrv: *const bindings::phy_driver,
> >>      ) -> crate::ffi::c_int {
> >>          // SAFETY: This callback is called only in contexts
> >>          // where we hold `phy_device->lock`, so the accessors on
> >>          // `Device` are okay to call.
> >>          let dev = unsafe { Device::from_raw(phydev) };
> >> -        T::match_phy_device(dev) as i32
> >> +        let drv = unsafe { T::from_raw(phydrv) };
> >> +        T::match_phy_device(dev, drv) as i32
> >>      }
> >>  
> >>      /// # Safety
> >> @@ -574,6 +577,19 @@ pub const fn create_phy_driver<T: Driver>() -> DriverVTable {
> >>  /// This trait is used to create a [`DriverVTable`].
> >>  #[vtable]
> >>  pub trait Driver {
> >> +    /// # Safety
> >> +    ///
> >> +    /// For the duration of `'a`, the pointer must point at a valid
> >> +    /// `phy_driver`, and the caller must be in a context where all
> >> +    /// methods defined on this struct are safe to call.
> >> +    unsafe fn from_raw<'a>(ptr: *const bindings::phy_driver) -> &'a DriverVTable {
> >> +        // CAST: `DriverVTable` is a `repr(transparent)` wrapper around `bindings::phy_driver`.
> >> +        let ptr = ptr.cast::<DriverVTable>();
> >> +        // SAFETY: by the function requirements the pointer is const and is
> >> +        // always valid to access for the duration of `'a`.
> >> +        unsafe { &*ptr }
> >> +    }
> > 
> > If we go the way of supplying a `&DriverVTable` in the
> > `match_phy_device` function, then this should be a function in the impl
> > block of `DriverVTable` and not in `Driver`.
> 
> Yeah.
> 
> > See my reply to Fujita on the previous version, I don't think that we
> > need to add the `DriverVTable` to the `match_phy_device` function if we
> > don't provide accessor methods. Currently that isn't needed, so you only
> > need the hunks above this one. (I'd wait for Fujita's reply though).
> 
> Agreed, to make DriverVTable actually useful in match_phy_device(),
> further changes would be needed. I think it's sufficient to simply
> make the Rust code compile, as shown in the patch below.
> 
> I can take care of making sure Rust uses DriverVTable correctly later.
>

Thanks a lot, I'm sending new revision with the below change as
suggested.

> diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
> index a59469c785e3..32ea43ece646 100644
> --- a/rust/kernel/net/phy.rs
> +++ b/rust/kernel/net/phy.rs
> @@ -421,6 +421,7 @@ impl<T: Driver> Adapter<T> {
>      /// `phydev` must be passed by the corresponding callback in `phy_driver`.
>      unsafe extern "C" fn match_phy_device_callback(
>          phydev: *mut bindings::phy_device,
> +        _phydrv: *const bindings::phy_driver,
>      ) -> crate::ffi::c_int {
>          // SAFETY: This callback is called only in contexts
>          // where we hold `phy_device->lock`, so the accessors on

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